Field of the Invention
The present invention relates to an imaging device, an imaging system, and a method for driving the imaging device.
Description of the Related Art
An imaging device is proposed which is configured so as to be capable of performing both of focus detection and imaging. According to Japanese Patent Application Laid-Open No. 2013-106194, one pixel of the imaging device includes a first photoelectric conversion portion and a second photoelectric conversion portion. Each of the photoelectric conversion portions is arranged so as to be approximately conjugated with a pupil of a lens. At the time of the focus detection, signals are independently read out from each of the first photoelectric conversion portions and the second photoelectric conversion portions in a plurality of pixels, and two images are generated by luminous fluxes which have passed through mutually different positions in the pupil of the lens. In addition, an image of an object can be obtained (imaged) by an operation of adding the signals of the two photoelectric conversion portions.
In Japanese Patent Application Laid-Open No. 2013-106194, an imaging device is also disclosed which is configured to have one common amplifier for the first photoelectric conversion portion and the second photoelectric conversion portion. It is disclosed that the above imaging device outputs a signal which corresponds to an electric charge of the first photoelectric conversion portion and a signal which corresponds to the sum of the electric charges of the first and the second photoelectric conversion portions.